98 psi is too high. Most fixture will have a max rating of 80 psi and 40 to 60 is sufficient for most homes.
I think if you have a pressure regulator on your main line then it is defective. probably a hole in the diaphragm by the 30 second rise from 40 to 98.

If you have a pressure reducing valve near the shut off valve you can take that down to about 60lbs and I think Joe is right about replacing the pressure release valve on the water tank.

Thanks Neal. Sorry to be dense but do mean replace the TPR valve on the side of the water heater or replace the wilkins valve on the hot water line. I'm thinking you mean the TPR because it should be releasing water with this high pressure problem and it is not. The wilkins valve is doing the release, thankfully. The pipe to the wilkins is warm and I can hear it running and the pipe to the TPR is cold with no running sound.

I do have a pressure reducing valve (cone shaped thing) at the point where water comes into the garage (where the water heater is located). I adjusted it counter clockwise a number of turns and it had very little effect on reducing static pressure. Only went down by 2lbs. Did at least 5 turns so it backed out a distance of 5mm. I'm afraid to back it out any more.

98 psi is too high. Most fixture will have a max rating of 80 psi and 40 to 60 is sufficient for most homes.
I think if you have a pressure regulator on your main line then it is defective. probably a hole in the diaphragm by the 30 second rise from 40 to 98.

I think you are right Joe. The pressure regulator is not working and has to be replaced. A job for this weekend.

Thanks Neal. Sorry to be dense but do mean replace the TPR valve on the side of the water heater or replace the wilkins valve on the hot water line. I'm thinking you mean the TPR because it should be releasing water with this high pressure problem and it is not. The wilkins valve is doing the release, thankfully. The pipe to the wilkins is warm and I can hear it running and the pipe to the TPR is cold with no running sound.

I do have a pressure reducing valve (cone shaped thing) at the point where water comes into the garage (where the water heater is located). I adjusted it counter clockwise a number of turns and it had very little effect on reducing static pressure. Only went down by 2lbs. Did at least 5 turns so it backed out a distance of 5mm. I'm afraid to back it out any more.

After you turned the regulator back, did you run water to relieve the pressure in the pipe?

After you turned the regulator back, did you run water to relieve the pressure in the pipe?

I saw a video online that said to run a faucet slightly while making the adjustment, so I did that. After I did the adjustment I turned on the faucet full for 10 seconds then closed it and went and checked the static water pressure.

Honestly, at 13 yo that tank is due to go away. Sediment, corrosion, and a failing PRV ... all point to a replacement. I just replaced a 13 yo tank and more than 50% of the thing was sediment ... it weighed a ton AFTER draining it!

New ones are more energy efficient, have better thermostats, and easy to install (if you have plumbing skills) ... GO FOR IT.

Honestly, at 13 yo that tank is due to go away. Sediment, corrosion, and a failing PRV ... all point to a replacement. I just replaced a 13 yo tank and more than 50% of the thing was sediment ... it weighed a ton AFTER draining it!

New ones are more energy efficient, have better thermostats, and easy to install (if you have plumbing skills) ... GO FOR IT.

Thank you CallMeVilla, that's a good point. I think after I have replaced the reducing valve I'll be thinking about that tank replacement as the next project. I think I can do it myself. What tank manufacturer did you go with.

Most recent replacement was with a Rheem. They wanted a 60 gallon version for the large family in their summer house. It has a "vacation" setting, so its energy use in minimized while they are gone. I receooended turning it off ... but they were fearful about re-lighting every trip.

You also have to know that tank manufacturers have their metallurgy down to a real science. For a 5-Year tank under normal usage it will die in 5 years +/- one month. Not kidding. I got home after replacing a 5-Year tank one day and my neighbor was hauling a new tank out of his truck. "Yeah, mine died within two months of the five year warranty." he said.